The present invention relates to a new and improved profiling apparatus for dressing a grinding wheel in a gear grinding machine.
In its more particular aspects the present invention relates to a new and improved profiling apparatus for a grinding wheel in a gear grinding machine which comprises at least one dressing tool for a substantially ring-shaped flank of the grinding wheel, axial and radial drive means for relative displacements between the dressing tool and the grinding wheel relative to the grinding wheel axis either in the direction thereof or at right angles thereto, and a control for matching or coordinating such relative displacements to each other such that the dressing operation is performed in corresponding with a desired or required profile of the flank of the grinding wheel.
In a profiling apparatus of this kind as known, for example, from German Patent Publication No. 2,140,978, published Mar. 30, 1982, only one dressing tool is provided which is arranged at a dressing unit or device. The dressing unit can be displaced parallel to and at right angles to the grinding wheel axis, whereas the grinding wheel is mounted to a stationarily arranged grinding spindle which only can be driven for rotation. No means are evident therefrom for compensating the wear of the dressing tool within the ambit of the control for the dressing unit. In order to control whether the dressing tool operates upon the entire surface of the grinding wheel intended to be dressed, there is measured the contact displacement of the dressing tool during each dressing stroke and the measured value is compared with a predetermined reference or set value. Further dressing strokes are performed until the two values conform to one another. For this control a signal transmitter is mounted with the dressing unit which responds to the contact of the dressing tool at the grinding wheel and generates an electrical signal. This signal is processed so as to form pulses which represent a measure of the contact time, and thus, the contact displacement of the dressing tool. The signals are added and constitute the actual value of the contact displacement path. A measure or dimension for the wear of the dressing tool can not be derived therefrom.
In a further prior art apparatus for dressing a ring surface of an axially repositionable or adjustable disk-shaped or dished grinding wheel in a gear grinding machine as known, for example, from German Patent Publication No. 2,726,843, published Nov. 9, 1978, and the corresponding U.S. Pat. No. 4,213,277, granted July 22, 1980, the position of the ring surface is controlled and the grinding wheel is repositioned in such a way that the ring surface stays at the same place independently of the wear. Such apparatus comprises an axially displaceable or advanceable dressing tool which is displaced along an arc-shaped path over the ring surface of the grinding wheel each time a dressing operation is performed. To that end, a lever which carries the dressing tool is pivoted about an axis which extends parallel to the grinding wheel axis. The ring surface of the grinding wheel which is to be dressed is scanned by a sensor or feeler which generates a signal each time the position of the ring surface deviates from a reference position. The signals from the scanner or feeler are transformed by control means into commands for displacing the grinding wheel and the dressing tool. Profiling of the grinding wheel in such a manner that the operative or working ring surface thereof could assume any desired profile possibly even deviating from a straight line, is impossible when using the known dressing device described hereinbefore.
However, in another profiling device for a grinding wheel in a gear grinding machine as known, for example, from German Patent Publication No. 3,112,084, published Mar. 4, 1982, two dressing tools are provided by means of which the flanks of a grinding wheel which substantially possesses the shape of a truncated cone can be dressed and provided with profile corrections. Each of the dressing tools is mounted at one end of a respective ram or plunger, the longitudinal axis of which extends in a plane which contains the grinding wheel axis. Each of the rams is longitudinally displaceable within a guide housing and is mounted for rotation. The two guide housings can be pivoted about a common pivot axis independently of each other. The common pivot axis extends in the central plane of the grinding wheel and at a distance from the grinding wheel axis. Both of the rams are designed as round toothed racks and mesh with a common pinion arranged on the pivot axis. At the end of each ram which is located remote from the dressing tool there is mounted a scanning or feeler arm which cooperates with a stencil which is exchangeably mounted to the associated guide housing in such a way that the relevant ram is rotated about its longitudinal axis during its longitudinal displacement. The associated dressing tool is thus pivoted about the longitudinal axis when the flank to be dressed at the grinding wheel is intended to be provided with a correction. During this correction the wear of the dressing tool is not taken into account.